An airplane for transport of passengers and freight usually comprises a single fuselage resting on the ground by means of a set of retractable landing gears, respectively two side gears and a front gear that is centered on a longitudinal median plane of the fuselage.
The fuselage usually is separated into two zones by a floor forming a main deck that extends over its entire length, respectively an upper zone in which a cockpit is laid out, placed in the front tip of the airplane, as well as the cabin for the passengers, and a lower zone that forms a hold for the baggage and varied cargo, this hold extending underneath the main deck, on a lower floor.
Each landing gear is articulated so as to come to be retracted, after takeoff, into a storage compartment that usually is placed under the wings for the side gears and under the front portion of the fuselage for the front central gear. This storage compartment is delimited by a structure that must be strong enough to withstand the stresses applied to the landing gear and it is equipped with flaps opening downward on the lower portion of the fuselage in order to unfold and retract the landing gear, while closing up again after takeoff in order to restore the desired aerodynamic form. It also constitutes the boundary between a pressurized zone inside the aircraft and a non-pressurized space accommodating the landing gear and therefore must be impervious and capable of withstanding the pressure difference between the pressurized space and the inside of the front gear compartment that is not pressurized.
The space around the front gear compartment, laid out underneath the main deck, generally serves as housing for various controls of the airplane. This space, however, is difficult to use because of its complex form, and a significant volume generally is wasted.